Resume is a document which represents you to your potential employer .therefore it should be designed in a professional and sincere manner. The resume speaks about the candidate's strengths and weaknesses and also provides the employer an insight into the candidate's professional history.. The resume acts as a door for you to get an interview withh the potential employer. The most important skill in the 21st century that a person needs to get a decent job is the computer skill. While specifying the computer skill you need to specify not only the skill that you posses but the level to which you have these skills. You should specify what different types of computer skills you have and to what extent you have these skills. For example a person applying for a secretary job can give her knowledge about computer skills as "proficient in MS office, preparation of charts etc".the following information is for people who sre applying for jobs in the US government. The form 171 has been replaced by a federal resume which is a 2-4 page document which contains various details about the applicant such as social security number, address, records etc. while applying for private companies people don't give their personal information. In the past this was considered as an important part of résumé. However it is a good practice to add your personal information to your resume even while applying for a private company as companies nowadays are very sensitive about security issues.
The thing to be considered while writing a resume is the size of the resume. Ideally it should be of one page. it can also extend to 2 pages. If you have got about 10 or more years of experience then you may have to extend the length of your résumé. The size of the resume may also depend upon the resume format you use. Resume formats are chronological and functional formats. a chronological resume is a resume that gives various details about the person in a chronological manner that is in a proper year wise way. This would be appropriate for many people. Functional resume is one which gives more importance to function or skills possessed by people. This is used as a cover-up for people who don't have a proper work record ie they would have shifted various jobs in a short span of time. There are people who use both these types of resumes. They combine both the types of resumes to enhance their skills at various periods of time. The type of resume that you prepare may depend upon the industry for which you have applied. For example incase of a sales job a brief description about you would fetch you an interview but in a managerial post this wont be possible.
The first and the most important thing to be prepared for getting an interview is the resume but the other things such as the covering letter must not be ignored. The covering letter must specify not only what is specified in the ad but also something extra. It makes your letter to standout from the crowd.